Angiogenesis is a multi-step developmental process that results in the formation of new blood vessels off of existing vessels. This spatially and temporally regulated process involves loosening of matrix contacts and support cell interactions in the existing vessels by proteases, followed by coordinated movement, morphological alteration, and proliferation of the smooth muscle and endothelial cells of the existing vessel. The nascent cells then extend into the target tissue followed by cell-cell interactions in which the endothelial cells form tubes which the smooth muscle cells surround. In a coordinated fashion, extracellular matrix proteins of the vessel are secreted and peri-endothelial support cells are recruited to support and maintain structural integrity (see, e.g., Daniel et al., Ann. Rev. Physiol. 2000(62):649, 2000). Angiogenesis plays important roles in both normal and pathological physiology.
Under normal physiological conditions, angiogenesis is involved in fetal and embryonic development, wound healing, organ regeneration, and female reproductive remodeling processes including formation of the endometrium, corpus luteum, and placenta. Angiogenesis is stringently regulated under normal conditions, especially in adult animals, and perturbation of the regulatory controls can lead to pathological angiogenesis.
Pathological angiogenesis has been implicated in the manifestation and/or progression of inflammatory diseases, certain eye disorders, and cancer. In particular, several lines of evidence support the concept that angiogenesis is essential for the growth and persistence of solid tumors and their metastases (see, e.g., Folkman, N. Engl. J. Med. 285:1182, 1971; Folkman et al., Nature 339:58, 1989; Kim et al., Nature 362:841, 1993; Hori et al., Cancer Res., 51:6180, 1991). Angiogenesis inhibitors are therefore useful for the prevention (e.g., treatment of premalignant conditions), intervention (e.g., treatment of small tumors), and regression (e.g., treatment of large tumors) of cancers (see, e.g., Bergers et al., Science 284:808, 1999).
The TWEAK protein, which has also been called TREPA and Apo3L, is a member of the tumor necrosis factor (TNF) family and is expressed in a wide variety of human tissues (Chicheportiche et al., J. Biol. Chem., 272(51):32401, 1997; see also Wiley, PCT Publication No. WO 98/35061, 13 Aug. 1998). Like most TNF family members, TWEAK is a Type II membrane protein with an extracellular C-terminal domain. Although TWEAK was originally described as a weak inducer of apoptosis, this induction of cell death was later shown to be indirect (Schneider et al., Eur. J. Immunol. 29:1785, 1999).
Lynch et al. demonstrated that TWEAK directly induces endothelial cell proliferation and angiogenesis (J. Biol. Chem., 274(13):8455, 1999). Picomolar concentrations of recombinant soluble TWEAK induce proliferation in multiple endothelial cell lines and in aortic smooth muscle cells, and reduce the requirement for serum and growth factors in culture. Moreover, TWEAK induces a strong angiogenic response in a rat corneal pocket assay. Since TNF family members initiate biological responses by signaling through members of the TNF receptor family, there has been great interest in identifying and characterizing a TWEAKR.
Marsters et al. reported that TWEAK binds to and signals through a death-domain containing receptor known variously as DR3, Apo3, WSL-1, TRAMP, or LARD (Marsters et al., Current Biology 8(9):525, 1998). Schneider et al., however, showed that TWEAK binds to and signals in Kym-1 cells but that Kym-1 cells do not express the receptor DR3 (Schneider et al., Eur. J. Immunol. 29:1785, 1999). These results suggest the existence of a yet to be identified TWEAK receptor.
Because TWEAK induces angiogenesis ill vivo, there is a particular need to identify the major functional TWEAKR. Once identified, TWEAKR may be used to screen for and develop TWEAKR agonists and antagonists for the modulation of angiogenesis and the treatment of human disease.
There is a need for additional compositions and methods of modulating angiogenesis for the prevention, abrogation, and mitigation of disease.